In a cellular wireless communication system, such as a code division multiple access (CDMA) system for instance, base stations are positioned throughout a coverage area and emit radio frequency radiation patterns that define cells. Mobile stations operating in a given cell may then wirelessly communicate with the serving base station, and the base station may provide connectivity with further network components such as switches and gateways that connect with transport networks.
In a CDMA system, each cell is typically divided into a number of sectors, each of which is identified by a specific pseudo-noise offset (i.e., “PN offset”) of a specific spreading sequence that is used to encode communications with mobile stations operating in the cell. At any given instant, a mobile station may thus operate in a given sector, and may thereby communicate with the serving base station using the PN offset of that sector. (In practice, an idle mobile station may communicate on a single PN offset (i.e., in a single sector) at once; an active mobile, on the other hand, might communicate on multiple PN offsets (i.e., in multiple sectors) at once, although a dominant one of those active PN offsets might be the focus of communications at any given moment.)
Unfortunately, in some wireless networks, the cells may not seamlessly cover an entire area, so there may be a hole in coverage between cells. To solve this problem, a wireless carrier may install a repeater that functions to extend the range of a given cell or sector, so as to fill in the hole in coverage. Such a repeater may be able to receive a signal distorted by transmission losses and to regenerate or replicate the signal. The repeater would include a donor antenna that would communicate with a base station, a coverage antenna that would communicate with mobile stations, and a build-out circuit that would boost communications from the base station to the mobile stations. For example, the repeater may be positioned between a mobile station and a base station to intercept signals sent between them. The repeater may amplify the power of these intercepted signals and send amplified versions of these signals to the mobile station or the base station. Therefore, the repeater may effectively extend the range of a given cell by boosting communications between a mobile station and a base station.
In practice, the donor antenna of a repeater may receive signals from multiple base stations and multiple base station sectors (i.e., signals with multiple PN offsets) at once and boost all of those signals. In addition, the repeater will receive signals from mobile stations, boost the signals, and radiate the amplified signals to all nearby base stations. However, radiating the amplified signals to all nearby base stations can decrease the capacity of base stations that are not the intended recipient of the amplified signals by increasing the ambient noise level. Furthermore, even if the donor antenna of the repeater is set to radiate to a single base station, when that base station becomes loaded with primary traffic from the system (e.g., traffic not from the extended coverage of the repeater) the repeater traffic can cause a decrease in the overall capacity of the base station due to the noise rise at the base station caused by the noise generated by the repeater.
It would therefore be desirable to have a repeater repeat signals from and to just one base station or to repeat signals from and to just one sector (one PN offset) of one base station with which the mobile station is in communication. It would be even more desirable to have a repeater determine the one base station or one sector to which it repeats signals. Furthermore, it would be desirable to have a repeater be able to change its donor base station by handing off communications from one base station to another that has less traffic, for example.